Pulse generating ring for electromagnetic rotary position detection

ABSTRACT

A pulser ring has cylindrical inner and outer rings nested together. The inner ring is formed at its one end with protrusions arranged at equal angular intervals. The outer ring is in the shape of a round comb and has its teeth engaged at a portion near the tip thereof in the grooves defined between the adjacent protrusions formed on the inner ring. The tip of each tooth protruding from the grooves is bent radially inwardly so as to engage the end face of the protrusion on the inner ring, thus coupling the inner ring and the outer ring together.

The present invention relates to a pulser ring for detecting the numberof revolutions of the front and rear wheels of an automobile to controlit by an antilock brake system (hereinafter referred to as ALB) and themethod for manufacturing the same.

The ALB is used to control the braking force according to the number ofrevolutions of the front and rear wheels of a car in order to preventthe wheels from locking and thus the car from skidding. Thus the ALBrequires detector means for detecting the revolving speeds of thewheels.

FIG. 13 shows a prior art detector for detecting the number ofrevolutions of a wheel. It comprises a pulse gear 3 press-fitted on anouter ring 2 of a wheel bearing 1 at its end, and an electromagneticsensor 4 arranged at a position opposite to the outer periphery of thepulse gear 3.

Such a prior art pulse gear 3 has been made of a steel material or asintered ferrous alloy. Corrosion-resistant treatment may be applied toits surface if necessary. Such a prior art pulse gear is thick in aradial direction and is heavy in weight. Further, the material cost aswell as production cost are rather high.

It is an object of the present invention to provide a pulser ring whichobviates the above said shortcomings, which can be mass-produced, andwhich is inexpensive, compact in size and light in weight, and toprovide a method for producing the same.

The inner ring and the outer ring pressed from a steel plate are coupledtogether so that the teeth on the outer ring will be received in thegrooves formed between the adjacent protrusions formed on one end of theinner ring. Each tooth has its tip bent inwardly and pressed against theend face of the inner ring. This minimizes the height of the pulse ringin the radial direction. Also, since the teeth are arrangedcircumferentially at equal intervals owing to the provision of theprotrusions, their pitch accuracy is high.

Further with this arrangement, the teeth of the outer ring can be heldso rigidly as not to be deformed easily even if they are hit by stonesand other foreign matter. Since the inner ring is located inside theteeth, the detection accuracy is improved. If the pulser ring is made ofstainless steel, the teeth will be protected against the possible attackof rust on the mounting shaft.

Other features and objects of the present invention will become apparentfrom the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of the pulser ring embodying thepresent invention;

FIGS. to 2 to 8 are explanatory views showing how the pulser ringaccording to the present invention is made;

FIG. 9 is an enlarged sectional view of the tip of one of the teethformed on the outer ring;

FIG. 10 is a partial vertical sectional view of the pulser ring of FIG.1;

FIG. 11 is a perspective view of a portion of the same;

FIG. 12 is a vertical sectional view showing how the same is used; and

FIG. 13 is a similar view of a prior art pulser ring in use.

Now referring to FIGS. 1 and 2, the pulser ring 11 according to thepresent invention comprises an inner ring 12 and an outer ring 13. Thelatter has comb-like teeth and is adapted to be fitted over the innerring 12. They are made by pressing separately of steel and coupledtogether.

The inner ring 12 is made of a corrosion-resistant magnetic stainlesssteel and shaped into a cylinder by pressing as shown in FIG. 1. Furtherit is formed at one end thereof with radially outwardly extendingprotrusions 14 formed by pressing. Grooves 15 are defined between theadjacent protrusions 14.

The outer ring 13 is made of the same material as the inner ring 12 andis formed with a plurality of axial teeth 16 arranged in acircumferential direction at equal intervals. Its end at the oppositeside of the teeth 16 is bent inwardly to form a flange 17. Each tooth 16is formed in its inner surface near its tip with a transverse notch 18.The teeth 16 are adapted to be bent along the notch 18 for caulking. Theouter ring 13 is also formed mainly by pressing.

Each protrusion 14 on the inner ring 12 has a width substantially equalto the distance between the adjacent teeth 16. Each groove 15 formedbetween the adjacent protrusions 14 has such a width that the respectiveteeth 16 of the outer ring 13 can snugly fit thereinto.

FIGS. 2 to 5 show the process for manufacturing the inner ring 12. Firstas shown in FIG. 2, a circular plate is drawn into a cup having a flange21 extending radially outwardly. The bottom 23 of the cup thus formed ispunched out so as to leave only its peripheral portion as a radiallyinwardly extending flange 22 as shown in FIG. 3. The flange 22 is spreadby use of a jig until it is flush with a cylindrical portion 24 of thecup (FIG. 4). Finally, the flange 21 is punched to form the grooves 15.The inner ring 12 thus made is shown in FIG. 5.

FIGS. 6 to 9 show the process for manufacturing the outer ring 13. Firstas shown in FIG. 6, a plurality of grooves 25 are formed along theperiphery of a circular plate at equal angular intervals by punching toform the teeth 16. Then the V-shaped notch 18 is formed in each tooth 16at its tip. The teeth 16 are bent at their base portion 26 by 90 degreesto form a cylindrical wall 27. The plate is thus formed into a cuphaving a bottom 28 (FIG. 7). Finally the bottom 28 is punched off,leaving an annular flange portion 17. The outer ring 13 thus made isshown in FIGS. 8 and 9.

The inner ring 12 and the outer ring 13 are inserted in a supporting die(not shown) one after the other so that the leading end of the innerring 12 will abut the flange 17 on the outer ring 13 and the tip of eachtooth 16 will be received in the respective groove 15 formed between theadjacent protrusions 14.

The inner ring 12 and the outer ring 13 may be coupled together beforeinserted in the supporting die.

After inserting both rings into the supporting die, a male press die isforced into the supporting die to bend or caulk the tip of the teeth 16inwardly against the end face of the inner ring 12 at the side of theprotrusions 14 to assemble the pulser ring 11 as shown in FIG. 10.

As shown in FIGS. 10 and 11, the inner ring 12 and the outer ring 13 arethus rigidly coupled together into the pulser ring 11 with the leadingend of the inner ring 12 in abutment with the flange 17 on the outerring 13 and the tip or caulking portion 16a of each tooth 16 of theouter ring 13 bent along the V-shaped notch 18 to extend inwardly.Further, since the teeth 16 have their tip fitted in the grooves 15formed between the adjacent protrusions 14 on the inner ring 12, the tworings are coupled together rigidly.

The teeth 16 of the outer ring 13 are formed first by punching a singleplate into a circular shape having a plurality of radial projectionsformed along its periphery and then by pressing the projections into acylindrical shape. The teeth 16 are held in position at their tip by theprotrusions 14 on the inner ring 12. Thus the rings 12 and 13 arerestrained from moving relative to each other in the circumferentialdirection and the teeth 16 can maintain its high pitch accuracy.

The inner ring 12 and the outer ring 13 may be punched from a singleplate at a time so that they are integral with each other. After foldingthem to overlap one upon the other, the inner ring 12 and the outer ring13 may be pressed into cylinders so that they are nested together withthe tip of each tooth 16 bent and overlying the end face of the innerring 12.

The pulser ring 11 thus made is press-fitted on a wheel bearing 1 aroundan outer ring 2 at its end as shown in FIG. 12. An electromagneticsensor 4 is provided at a position opposite to the outer periphery ofthe pulser ring 11.

When the pulser ring 11 rotates together with the outer ring 2,electromotive forces are produced from the circumferentially arrangedteeth 16. The sensor 4 picks them up to determine the number ofrevolutions of the wheel bearing 1.

With such a pulser ring, it is required that the pitch error of itsteeth 16 as well as error of diameters of both rings be as small aspossible. With the pulser ring 11 according to the present invention,the teeth 16 can be pressed from a single plate at one time. Each tooth16 has its tip snugly fit in the respective groove formed between theadjacent protrusions on the inner ring. Thus the pitch error of theteeth 16 is reduced to a minimum. Moreover, since the inner ring 12 andthe outer ring 13 are formed into cylinders by pressing, the precisionof diameters of both rings will be improved, thus increasing thedetection accuracy.

What is claimed:
 1. A pulser ring comprising an inner ring made from asteel plate, and an outer ring made from a steel plate, said inner ringbeing formed at one end thereof with a plurality of protrusions equallyangularly spaced therebetween and extending radially outwardly, saidouter ring being formed with a plurality of teeth arranged with equalangular spacings so as to extend axially, said outer ring being fittedon said inner ring with said teeth on said outer ring held in groovesformed between said protrusions on said inner ring, the tips of saidteeth bent inwardly against the end of said inner ring to couple saidouter ring with said inner ring.